Structured surfaces that contain flowable materials in specific patterns have proven to be useful in a variety of applications. For example, radio frequency identification (RFID) tags, cellular telephones and computers often contain flexible electrical micro-circuit boards that are formed by depositing a metallic nano-paste into a structured surface. Color filters, used in television screens, are formed by depositing specifically colored inks onto a structured surface so that the inks are contained in a specific area. Although these products have varying applications and uses, all begin with a structured surface that has the ability to contain a flowable material within a defined area. Thus, there has been a great deal of research done to devise processes that efficiently manufacture highly resolved structured surfaces.
One known method of forming structured surfaces utilizes photolithography. This method requires the steps of covering a photosensitive resin with a mask, blanket exposing the photosensitive resin to ultraviolet radiation, and then further developing the exposed photosensitive resin. A method of forming an integrated circuit using photolithography is reported in U.S. patent application No. 2003/0059987 to Sirringhaus. A method of forming a color filter using this method is reported in U.S. Pat. No. 6,455,209 to Okaniwa et al. A method of forming an electro-luminescent (EL) element using this method is reported in U.S. Pat. No. 6,610,552 to Fujimori et al.
Another known method of forming structured surfaces utilizes an etching process. In this method a photosensitive resin is applied to a layer of metal on a substrate. The photosensitive resin is then lithographically imaged, as described above, so as to expose certain areas of the metal layer underneath the photosensitive resin. The exposed areas of the metal layer is then removed by bathing the entire assembly in an etchant. In this method, the photosensitive resin acts as a resist for the metal layer. A method of forming a color filter using this etching method is reported in EP 1 061 383 to Seiko Epson.
Structured surfaces may also be manufactured using a known thermal transfer process, as reported in EP 1 226 974 to Seiko Epson. In a thermal transfer process, a donor sheet and an image receiving element are placed in contact with each other so that when the donor sheet is exposed to infrared radiation, the transfer layer of the donor sheet transfers to the image receiving element, thus forming a structured surface on the image receiving element.
Still another method of forming structured surfaces involves molding a flowable polymer. In this method, the flowable polymer is brought in contact with a molding surface to form structured patterns. The flowable polymer is then solidified and separated from the molding surface. This method is reported in U.S. Pat. No. 6,375,871 to Bentsen et al.